1. Field of the Invention
The present invention relates to a semiconductor device including an insulation film and a fabrication method thereof More particularly, the present invention relates to a semiconductor device including an insulation film such as an interlayer insulation film or a passivation film superior in water resistance, and a method of fabrication thereof.
2. Description of the Background Art
In the past few years, intensive efforts have been taken to reduce the size of interconnections and provide multilayers for the purpose of further increasing the integration density of semiconductor integrated circuit devices. An interlayer insulation film is provided between each interconnection to obtain a multilayer structure of the interconnection. If the surface of this interlayer insulation film is not planar, a step-graded portion will be generated at the interconnection formed above the interlayer insulation film. This will cause defects such as disconnection. Therefore, the surface of the interlayer insulation film (the surface of the device) must be made as flat as possible. The technique to planarize the surface of the device is called planarization. This planarization technique has become important in reducing the size and providing multilayers of the interconnection.
In planarization, an SOG (Spin On Glass) film is known as an interlayer insulation film that is generally used. Recently, development in the planarization technique taking advantage of the fluidity of a material of the interlayer insulation film is particularly noticeable.
An xe2x80x9cSOGxe2x80x9d is a generic term of a film mainly composed of a solution in which a silicon compound is dissolved in an organic solvent, and silicon dioxide formed from that solution.
In forming an SOG film, first a solution having a silicon compound dissolved in an organic solvent is applied in droplets on a rotated substrate. By this rotation, the solution coating is provided so as to alleviate the step-graded portion on the substrate corresponding to the interconnection. More specifically, the coating is formed thick at the concave portion and thin at the convex portion on the substrate. As a result, the surface of the solution coating is planarized.
Then, heat treatment is applied to vaporize the organic solvent. Also, polymerization proceeds to result in a planarized SOG film at the surface.
An SOG film is typically classified into an inorganic SOG film that does not include any organic component in a silicon compound, as represented by the following general formula (1), and an organic SOG film including an organic component in a silicon compound, as represented by the following general formula (2).
[SiO2]nxe2x80x83xe2x80x83(1)
[RxSiYOZ]nxe2x80x83xe2x80x83(2)
(n, X, Y, Z: integer; R: alkyl group or aryl group)
An inorganic SOG film includes a great amount of moisture and hydroxyl group. It is more brittle than a silicon oxide film formed by CVD (Chemical Vapor Deposition). There was a disadvantage that a crack is easily generated during the heat treatment when the thickness of the inorganic SOG film is greater than 0.5 xcexcm.
In contrast, an organic SOG film does not have any cracks generated during the heat treatment, and the film thickness can be set to approximately 0.5-1 xcexcm. Therefore, the usage of an organic SOG film allows the formation of a thicker interlayer insulation film. This means that sufficient planarization be achieved even for a great step-graded portion on a substrate.
As described above, inorganic and organic SOG films have superior planarization. However, the great amount of moisture and hydroxyl group included in an inorganic SOG film will adversely affect the metal interconnection and the like to induce the problem of degrading the electrical characteristics and the action of corrosion.
A similar problem is seen in an organic SOG film. This is because, though smaller in comparison to an inorganic SOG film, the organic SOG film includes some amount of moisture and hydroxyl group.
To compensate for this disadvantage when an SOG film is employed as an interlayer insulation film, an insulation film such as a silicon oxide film formed by, for example, plasma CVD, having the characteristics of insulation and mechanical strength in addition to the property of blocking moisture and hydroxyl group is provided above or beneath the SOG film. Such a structure is disclosed in, for example, Japanese Patent Laying-Open No. 5-226334.
An object of the present invention is to provide a semiconductor device that has sufficient water resistance.
Another object of the present invention is to provide a semiconductor device that allows the adhesion intensity between an upper insulation film and a lower insulation film to be improved.
A further object of the present invention is to provide a semiconductor device that can have interconnection resistance reduced of a metal interconnection layer located below an insulation film.
According to an aspect of the present invention, a method of fabricating semiconductor device includes the steps of forming a first insulation film on a substrate, forming a cap film on the first insulation film having water resistance better than that of the first insulation film, and introducing impurities into the first insulation film.
By introducing impurities such as by ion-implantation into the first insulation film, the film property of the first insulation film is improved to reduce the moisture and hydroxyl group included in the film. Also, the first insulation film having impurities introduced will be superior in hygroscopic resistance. By forming a cap film on the first insulation film having water resistance favorable than that of the first insulation film, the containing rate of moisture and hydroxyl group in the first insulation film is reduced.
Introduction of impurities into the first insulation film can be carried out through a cap that is formed. Introduction through the cap film allows the containing rate of the moisture and hydroxyl group in the first insulation film to be reduced significantly. The cap film can be formed after introducing impurities into the first insulation film. By applying a heat treatment after introducing the impurities, the moisture remaining in the insulation film can be removed promptly.
The substrate is typically a semiconductor substrate such as of single crystal silicon. However, the substrate may be an insulation substrate such as a glass substrate. The first insulation film includes a planarized insulation film that is subjected to, for example, a planar process. As one example, the first insulation film includes a silicon oxide film containing at least 1% of carbon atoms. As another example, the first insulation film includes an inorganic SOG film. The impurities introduced into the first insulation film are preferably boron ions or argon ions. The cap film preferably includes a silicon nitride type material. As one example, the cap film includes a nitride film that is the first insulation film nitrided. As another example, the cap film may be a metal film.
According to another aspect of the present invention, a method of fabricating a semiconductor device includes the step of forming a lower insulation film on a substrate prior to formation of a first insulation film. Introduction of impurities into the first insulation film is carried out under the condition that the introduced impurities arrive at the interface between the first insulation film and the lower insulation film. Such introduction of impurities under this condition allows greater adhesion to be obtained between the first insulation film and the lower insulation film. Particularly, by introducing impurities under the condition where the number of impurities per unit area passing through the bottom plane of the first insulation film is at least 2xc3x971013 atoms/cm2, superior adhesion intensity can be obtained. The upper limit of the number of impurities passing through the bottom plane of the first insulation film per unit area is preferably 2xc3x971018 atoms/cm2.
According to a further aspect of the present invention, a method of fabricating a semiconductor device includes the step of forming a metal interconnection layer on a substrate prior to formation of a first insulation film. Introduction of impurities into the first insulation film is carried out under the condition that the introduced impurities reach the metal interconnection layer. By introducing impurities such as boron into the metal interconnection layer, the interconnection resistance is reduced. As a result, the thickness of the interconnection member can be made thinner. Boron ions have a relatively small mass. Therefore, when implanted under the same implantation energy, boron ions will be implanted deeper than those of greater mass. Therefore, the effect of modifying the property of the insulation film can be improved.
According to still another aspect of the present invention, a method of fabricating a semiconductor device includes the steps of forming a metal interconnection layer on a substrate, and forming a lower insulation film on the metal interconnection layer, prior to formation of a first insulation film. Introduction of impurities into the first insulation film is carried out under the condition of the introduced impurities reaching the metal interconnection layer.
By using a layered film of a first insulation film and a cap film, or a layered film of a lower insulation film, a first insulation film, and a cap film as a interlayer insulation film or a passivation film, the water resistance of the semiconductor device can be improved significantly.
The semiconductor device of the present invention includes a substrate, a first insulation film located on the substrate, a cap film covering the first insulation film, and having water resistance favorable than that of the first insulation film, and impurities distributed in the first insulation film and in the cap film.
The cap film preferably includes a silicon nitride type material. As one example, the cap film includes a nitride film that is the first insulation film nitrided. As another example, the cap film may be a metal film.
The first insulation film preferably includes a planarization insulation film that is subjected to a planarization process. As one example, the first insulation film includes a silicon oxide film containing at least 1% of carbon atoms. As another example, the first insulation film includes an inorganic SOG film.
The impurities are preferably either boron or argon ions. The number of impurities introduced into the first insulation film is preferably at least 2xc3x971013 atoms/cm2.
According to a still further aspect of the present invention, a semiconductor device includes a lower insulation film below the first insulation film. The impurities are also introduced into the lower insulation film. The profile of the impurities is continuous with the lower insulation film and the first insulation film. The number of impurities introduced into the first insulation film is preferably at least 2xc3x971013 atoms/cm2.
According to yet a further aspect of the present invention, a semiconductor device includes a metal interconnection layer below the first insulation film. Impurities are introduced also into the metal interconnection layer. The metal interconnection layer preferably includes a titanium film to which impurities are introduced.
According to the semiconductor device of the present invention, the film property is improved by introducing impurities into the first insulation film. The moisture and hydroxyl group in the film are reduced to improve the hygroscopic resistance. Since the cap film located on the first insulation film includes impurities and has water resistance superior than that of the first insulation film, the containing rate of the moisture and hydroxyl group in the first insulation film is further reduced.
The impurities introduced so as to pass through the bottom plane of the first insulation film do not have to pass through the entire bottom plane of the first insulation film. The introduced impurities have to pass through only at least a portion of the bottom plane of the first insulation film.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.